Technology

Fibre-optic sensing? How does that work?

When light travels along a fibre-optic cable, the way it “scatters” light along the fibre enables us to detect changes in external conditions at every point along the entire length of the fibre. Using sophisticated lasers and special interpretation software, very precise real time information can be derived on external temperature. Alquist’s Celsius system uses the Rayman Scattering effect, combined with measurement of the Stokes/anti-Stokes ratio of light intensity, to calculate temperatures every metre along fibre optic cables extending many kilometres.

This remarkable technology has been deployed extensively in the oil and gas sector, using temperature differentials between the top and bottom of oil and gas pipelines to monitor product flow and leaks. It is also used to monitor heat-build up in power transmission cables. Installations often cover hundreds of miles of pipeline and cable, in hostile and inaccessible terrain. Alquist Consulting is a market leader in providing interpretation and calibration software to manage these deployments.

How does it compare with other temperature monitoring systems?

Fibre-sensing has significant advantages over wired and wireless temperature monitoring systems. No other technology competes in terms of cost, resilience and simplicity:

low cost: for large deployments the cost per sensing point is extremely low

resilience: the fibre has an expected service life of 30 years, with special encasements available for harsh environments.

simplicity: one single fibre and laser unit can monitor many different environments and conditions

low maintenance: if properly installed the fibre requires almost zero maintenance. There is nothing to wear out, no batteries to replace, no problems with radio signal interference or power supply

passivity: fibre-optic cable does not have any electrical properties, and is inert, making it safe to deploy in sensitive environments